The invention is directed to a paper guide means for printer equipment and, in particular to a paper guide means for conveying and positioning recording media in printer equipment, having a friction drive that conveys the recording medium and which is composed of a conveyor drum and of at least one roller carrier having appertaining paper pressing rollers and also having a trough-shaped paper guide element adapted to the conveyor drum that, together with the conveyor drum forms a guide channel for the recording media to be printed.
Apparatus of this species are notoriously known and have also been successfully employed for the greatest variety of design types of printer equipment situated in the marketplace. The most critical component parts of such paper guide means are thereby a paper carrier fashioned as a paper drum, generally a paper guide trough that is combined with paper guide rollers and is arranged under the platen such that the page to be printed that is pulled through under the platen from behind can be guided to the front into the region of the printing line.
German Utility Model No. 80 06 325 discloses a paper infeed means for printer equipment comprising a paper carrier fashioned as a paper drum and comprising a paper guide trough that has paper pressing elements and presses resiliently against the paper drum. The paper guide trough is thereby composed of a rigid roller carrier having four paper pressing rollers arranged thereon. Centrally attacking lever arrangements are attached to these paper pressing rollers. As a result of such a Cardanic suspension of the roller carriers, the paper pressing rollers press uniformly against the paper drum or, respectively, against the recording medium conducted therebetween.
DE-A No. 1-36 32 863 discloses a paper detector for a printer means having two paper guides. The paper detector comprises a reflected light sensor having a light transmission element that emits light to one of the two paper guides and having a light reception element that receives the light reflected by the paper situated in this one paper guide. Over and above this, a detector lever is provided that is moved when paper is introduced into the other paper guide. The detector lever then in turn moves a reflection plate into a position in which it covers the front side of the light sensor and the light from the light transmission element is reflected to the light reception element. The light sensor facing toward the one paper guide is in the position to identify whether paper is introduced into this paper guide or not. When the paper is introduced into the other paper guide, the reflection plate is pushed in front of the light sensor as consequence of the motion of the detector lever, so that the light coming from the light sensor is reflected by this reflection plate. In this way, a determination can be made via the reception of the light reflected in this way whether paper is present in the other paper guide or not.
U.S. Pat. No. 2,218,108 discloses a paper feed mechanism for a typewriter that has a paper guide element in the form of a metallic plate adapted to the contour of the platen. Together with the platen, the guide element limits a guide channel for the recording media and comprises clearances into which paper conveying rollers partially extend and press the recording paper against the platen.
DE-C2 32 14 549 also discloses a conveyor means for margin-perforated fanfold paper and for continuous roll paper, whereby the pressure rollers are pressed against the platen with a spring. In order to be able to set a different pressing power corresponding to the selected type of recording medium - fanfold paper or continuous roll paper -, a lever having a first and having a second lever arm is provided. This lever can be pivoted in the direction of the axis of the platen such that the lever exerts no influence on the pressing power in the one position for operation with fanfold paper and, in the other position, the second lever arm blocks the paper web of the fanfold paper and the first lever arm exerts an additional pressure onto the spring in the direction of the platen.
Given employment of such apparatus, however, the paper conveying and paper guiding parts are individually introduced, set and secured in the printer frame.